Annu. Rev. Astron. Astrophys. 1984. 22: 185-222 Copyright © 1984 by Annual Reviews. All rights reserved

5. LOOKING FORWARD TO LOOKING BACK

Astronomers have an advantage over other historians: they can observe history directly-if not their own, at least someone else's. Substantial gains in detector technology have recently enabled photometric and spectroscopic measurements of average luminosity galaxies at redshifts approaching unity. This means that we can now view galaxies half as old as local galaxies.

This review article has concentrated on traditional approaches to the study of galaxy evolution, which involve looking at the structure, dynamics, and the stellar/gas content of present-epoch galaxies in order to test models of formation. Including the dimension of time will greatly enhance our ability to choose among models - for example, to discover if S0 galaxies have been dormant in star formation for more than the last few billion years. (Consider how much more difficult it would be to study stellar evolution if only old galactic globular clusters could be observed.)

It would be presumptuous to consider this last section a review. The subject is too young and too confused to allow anything more than an introduction to what should become the most powerful tool in the study of galaxy evolution. The discussion is divided into two sections, photometry and spectroscopy, which, as usual, reflect the choice between obtaining a small amount of information for a large number of objects or vice versa.